Well folks, I’m back at it again. This time more determined than ever. We can rebuild it, stronger, faster, better than ever. Armed with my trusty HydroBuddy, we have the technology.
With my first (sort of… there have been more) failure under my belt, and 3 weeks until I kickoff my next grow, I’m back to the books and ready to reboot. So, fellow Jacks/Peters 321 abusers, let’s try this again.
At this point, you might be asking, why mess with a good thing? OCD my friends… that and the unwillingness to pay more money for the same chemicals with fancy marketing. You read that correctly, I’m cheap, but mama didn’t raise no fool. Here’s what I think can be improved:
Same NPK in veg and flower? We can certainly do better than that…
- Too much K in veg.
- Not enough N in veg.
- Not enough K in flower
- Too much N in flower?
- Not enough S in flower
- Not engineered for coco
Let’s lay some ground rules, and find some targets for the next experiment. First thing is first, and that is to answer the question: why did I fail last time? Well things went well for a while, but eventually symptoms showed problems on the K/Ca/Mg front. In part, I think I wasn’t getting enough runoff from my feeds, but even then, the buildup wasn’t terrible when I measured after a flush. After doing a bunch of reading today, I found something that clicked. The answer comes once again from… MULDERS CHART!!!
Mulder’s chart is a chemistry-oriented approach to analyzing nutrient interactions. It tells us that all nutrients are inextricably linked. One cannot simply increase the presence of one nutrient, without affecting potentially several others.
While I knew that K, Ca and Mg all interact, because they are all positive ions, I didn’t have the frame of reference to know what ratios are reasonable. Today, I found that link and it made sense.
…Applying too much calcium and magnesium can cause a potassium deficiency; the K/Ca and K/Mg ratio should always be kept above 2 (but below 10, since too much K can hinder the absorption of calcium and magnesium). Too much potassium can also prevent the absorption of certain micro-elements, such as zinc. It is particularly important to take account of this interaction when using very hard water with a high calcium and magnesium content.
I think that will provide the pivotal frame of reference that I was missing. Adding this constraint will certainly make our designer nutrient more challenging to accomplish, but we must press on.
So here’s a few things I know about nutrients and coco, that will help us determine how to design a custom Jacks/Peters-based formula that beats 321.
- New coco substrates hold significant quantities of K
- New coco substrates replace K in bonding sites in favor of Ca and Mg (initially depletes Ca/Mg, adds K)
- Our K:Ca ratio needs to be no less than 2:1 and no more than 10:1
- Our Ca:Mg ratio needs to be around 2:1 to 4:1
- Cannabis (and all plants) use more Ca than P, so set Ca > P
- Sulfur may be beneficial in flower for the production of terpenes
- Cannabis needs more N in veg and more K in flower
According to my HydroBuddy, the 321 formula comes out to a ratio of 3-2-5-2.5-1.25 N-P-K-Ca-Mg.
For those who haven’t used 321, it’s 3.6g Peters 5-11-26, 2.4g Calcinit, 1.2g Epsom.
Already, we can see that this hits the 2:1 K:Ca ratio right on the head, and also a 2:1 Ca:Mg ratio. Target ratios right where we expected them. So lets go about trying to figure out a veg formula.
I’ve done a sampling of the internet in days passed. Some very knowledgeable growers (f@tman?) have suggested that 3-1-2 is ideal for veg. I think that this is not a bad starting point. We have lower K initially, to deal with the problem of K already in the substrate, and more N.
Let’s add in our Ca and Mg to this at 2:1. Since we know that coco will deplete this initially, I think we want Ca as high as possible.
That would put us at:
3-1-2-1-0.5 N-P-K-Ca-Mg – however with early life Ca deficiencies, I think I want more.
A small tweak allows us to pull up the Ca:
So… how do we achieve this. Well, one idea is to drop the Epsom in favor of Mag Nitrate. That will boost our N, and drop S, which we aren’t too concerned about right now. Unfortunately, hydro buddy says this doesn’t get us close enough. We could do it with ammonium nitrate, but because of it’s explosive potential, it’s not available in the US to the general public.
If we drop N/K relative to P, let’s see if we can make it work:
For this to happen, we will need to use ammonium sulfate. There’s a lot of bad press about ammonium, but in the right ratios, it may turn out to be beneficial for this reason:
Knowing that ammoniacal nitrogen drops pH three times faster than nitrate nitrogen raises it, the water-soluble grower can mix ammonium sulfate with calcium nitrate and/or potassium nitrate to achieve a 1:3 ratio of ammonium to nitrate nitrogen. As plants uptake these two nitrogen forms, the opposing pH pressures cancel each other out, resulting in low to no pressure on pH.
Interesting… as long as we keep it in ratio, it might actually help balance out the nitrates, which tend to increase pH at the root zone.
This roughly works out, close to targets. So, for the veg formula, I’ve removed epsom, and added ammonium sulfate and magnesium nitrate. Additionally, I’ll use TM-7 to make up the micronutrient difference for any reduction in the amount of Peter’s used.
Here’s the mix:
Base Peters 5-11-26 -- 24g Calcium Nitrate -- 16g Additives Magnesium Nitrate -- 8g Ammonium Sulfate -- 6g X TM-7 (removed)
And here’s the results:
Not bad – we hit our 3:1 NO3:NH4, our 2:1 K:Ca and pretty close to a 2.5-1-2.5 ratio. This is pretty reasonable. I’m glad to see that peters and calcium nitrate balanced out to 3:2 as well. That’s inspiring. Without running some plants, I can’t think of any way to improve it, so I think this is a reasonable formula to test.
Next post, I’ll try to figure out a formula for bloom.